With less than six months to go before the start of the 2016 Rio Summer Olympics, Brazil has become the focal point of the mosquito-borne Zika virus.
Here is what we know so far about the virus, and what preparations are being made to protect athletes ahead of the Games.
Q: How does the virus spread and what are its consequences?
A: The virus is transmitted by the Aedes aegypti mosquito, which is also responsible for spreading two more widespread and potentially fatal diseases -- yellow fever and dengue fever -- as well as the debilitating chikungunya. Medical experts currently estimate that only 20 percent of people who are infected with Zika develop outward symptoms, including a flu-like fever, joint pain, skin rashes and reddened eyes that may last a week. Strong evidence has emerged indicating a link between Zika and the birth defect microcephaly, which causes children to be born with abnormally small heads and underdeveloped brains. Nearly 4,000 cases have been diagnosed in Brazil as of last week. Researchers are also exploring a link between Zika and Guillain-Barre Syndrome, an autoimmune disease that attacks the nervous system and can cause paralysis.
Zika first emerged in Africa in the late 1940s, and only recently has traveled or "vectored" to Europe, Asia, the Americas (including the United States, where cases have been diagnosed in 21 states and the District of Columbia as of this week) and some Pacific islands. Some researchers have speculated that Zika got a stronger foothold in Brazil during the 2014 World Cup, and the first case was diagnosed there in May 2015. Risk for other routes of transmission, including bodily fluids and sexual contact, has not been firmly established. The World Health Organization recently declared Zika a "global health emergency.'' Thus far, pregnant women are being advised not to travel to Brazil, and women who are trying to conceive should exercise great caution while visiting.
President Barack Obama has asked the U.S. Congress for $1.8 billion in emergency funding to combat the epidemic. Leading U.S. infectious disease experts have said the best-case timetable for development of a vaccine would see clinical trials start this year, but approval for the general public could be years away.
Q: What is the U.S. Olympic Committee telling its prospective Rio athletes and staff?
A: In addition to consulting with the Centers for Disease Control and the World Health Organization on the evolving situation, the USOC announced last week it would hire two infectious disease experts as advisors and intends to pay particular attention to recommendations for women of childbearing age. As first reported by USA Today, the USOC sent a letter to all athletes competing for spots on the team, informing them of the hires and a publicly accessible online resource for information as it becomes available.
In a recent interview with ESPN.com, USOC CEO Scott Blackmun said he has not been part of any discussions about a worst-case scenario in which the Summer Games would be delayed or moved. He did acknowledge that the rapidly evolving public health issue is materially different from now-standard pre-Games concerns of security and terrorism, transit and venue completion. "I think that's a fair comment," Blackmun said. "I think we believe that we're going to know a lot more about Zika in three months than we do today."
Q: Could poor water quality and pollution in Rio de Janeiro contribute to the proliferation of the virus-carrying mosquito?
A: The short answer is they are not directly connected. The Aedes aegypti mosquito likes clean water as well as dirty -- anything that collects in containers people leave around, as well as standing puddles. Joseph Eisenberg, a University of Michigan School of Public Health professor of epidemiology who has done research in South America, called it "a household mosquito" that likes to breed in flower pots and other objects on porches and in backyards.
William Pan, a Duke University assistant professor of global environmental health, wrote in an email to ESPN.com: "Some pollution actually prevents mosquito reproduction -- but it is mostly oil-based spills where the larvae suffocate because they cannot break the oil barrier. Sewage doesn't do this, but significant changes in water quality can reduce breeding. Poor water quality in general can increase breeding -- there is a fine line that depends a lot on the mosquito species, level of pollution and local ecology."
Q: What measures are Rio 2016 organizers taking to protect athletes and visitors at the Summer Games?
A: Organizers say they are already inspecting Olympic venue facilities and areas for standing water and fumigating in some cases, and will do those inspections on a daily basis during the Games. Scheduled for Aug. 5-21, the Games fall within a cooler, drier season when the prevalence of mosquitos is much lower.
Certain precautions are already being made at the golf venue, which is west of Ipanema Beach. Ty Votaw, the PGA Tour's chief marketing officer and vice president of the International Golf Federation which coordinated the effort to return golf to the Olympics, told ESPN.com that the IGF has been in contact with the IOC and CDC and various other groups regarding the Zika virus "to get a sense of the situation so we can fully educate our players. Our athletes' safety is our ultimate priority.''
Given that there are water hazards on the course, Votaw said, "We are working to make sure that there is movement in the water in those lakes and ponds. A form of reverse irrigation can be used to make sure the water is not sitting, doesn't become stagnant.''
Many precautions will be up to individuals -- wearing clothing that covers arms and legs, using insect repellent and sleeping with windows closed. The Brazilian government is conducting a national education and eradication campaign, mobilizing military and civilian personnel to go door-to-door with leaflets.
Q: What are U.S. athletes saying?
A: U.S. soccer goalkeeper Hope Solo made headlines when she said she would opt out of Rio if the Games were about to begin. Most athletes -- and women are getting more questions, for obvious reasons -- have had more measured responses. On the eve of the U.S. Olympic Team Trials Marathon in Los Angeles, 2008 and 2012 team member Shalane Flanagan said each Games lead-up is accompanied by its own concerns and she has learned not to worry. "I find that the countries rise to the occasion and make things great for the athletes," she said. "Every [Olympic] site has exceeded my expectations."
ESPN.com golf writer Bob Harig contributed to this story.